As recording media for recording data of, e.g., personal computers, 2HD flexible discs (hereinafter referred to as “2HD-FD”), which are flexible magnetic discs, are now widely used, and a disc drive for 2HD-FD is carried in many personal computers as a standardized equipment. However, in recent years, the amount of data to be dealt with greatly increases, and the recording capacity of 2HD-FD is no longer sufficient in many cases. Accordingly, the increase in capacity of a flexible magnetic disc capable of easily handling is desired.
To meet the requirement, various techniques for the purpose of increasing the recording capacity of magnetic recording media have been developed and flexible magnetic discs far exceeding the recording capacity of 2HD-FD, e.g., magnetic discs having a recording capacity of 100 MB or higher, have been put to practical use. To cope with high density recording of data and data transfer at a high speed, recording and reproduction of these high capacity magnetic discs are performed with a magnetic disc apparatus using a magnetic head.
As is already known, there are cases where very important data (information) are recorded on magnetic discs, and recording and reproduction of data are generally performed repeatedly. Accordingly, it is of course required of high capacity magnetic discs to have excellent durability. Further, in recording and reproducing data, the load applied to the magnetic head of a magnetic recording apparatus is preferably smaller. For these requirements, coming of a magnetic disc having more excellent characteristics is required.
When a magnetic disc is revolved at a high speed and a magnetic head is run for seeking the surface of the disc for the prescribed time (e.g., from 200 to 300 hours in high temperature environment), there is a case where the magnetic disc takes a scratch and data cannot be recorded or reproduced, which leads to the occurrence of an error. One cause of the occurrence of scratches on a magnetic disc is the evaporation of a lubricant due to running and the reduction of a lubricating function.
It is disclosed in JP-A-2002-74649 (The term “JP-A” as used herein refers to an “unexamined published Japanese patent application”.) that in the magnetic disc disclosed in the patent comprising a magnetic layer having provided on an intermediate layer, an appropriate amount of alkylamine lubricant is supplied to the surface of the magnetic disc without being adsorbed onto the nonmagnetic powder contained in the intermediate layer, so that the reduction of a friction coefficient can be realized without deteriorating electromagnetic characteristics and excellent reliability of the magnetic disc can be ensured.
Further, it is shown in EXAMPLES of JP-A-2003-16638 that the durability of a medium can be improved by reducing the frictional force applied to a magnetic head. However, it is known that a frictional force increases when the relative velocity between a head and a medium lowers, so that it is necessary to secure proper frictional characteristics in a wide range of relative velocity for ensuring stable frictional characteristics from the inside diameter to the outside diameter of a magnetic disc. Further, it has been known that when the value of frictional force is greatly different at the radius position, the attitude of a head changes, the spacing loss between a head and a disc becomes great and electromagnetic characteristics lower. This tendency is conspicuous when recording density is high, so that the improvement of durability was out of the question in the recording/reproducing system as attained in JP-A-2003-16638 having a track breadth in reproduction of 5 μm or more.